1. Field of the Invention
The present invention relates to a piezoelectric material, and more particularly, to a lead-free piezoelectric material and a production method therefor. The present invention also relates to a piezoelectric element using the piezoelectric material, a multilayered piezoelectric element, a liquid ejection head, a liquid ejection apparatus, an ultrasonic motor, an optical equipment, a vibration apparatus, a dust removing apparatus, an imaging apparatus, and an electronic equipment.
2. Description of the Related Art
A commonly used piezoelectric material is an ABO3 perovskite-type metal oxide such as lead titanate zirconate (hereinafter referred to as “PZT”). However, PZT contains lead at an A-site of a perovskite skeleton. Accordingly, an effect of a lead component on environments has been seen as a problem. In order to deal with this problem, a piezoelectric material and a piezoelectric element using a lead-free perovskite-type metal oxide have been proposed.
For example, as a piezoelectric material formed of a lead-free perovskite-type oxide, Japanese Patent Publication No. H04-60073 discloses a Bi0.5Na0.5TiO3—BaTiO3 based or Bi0.5Na0.5TiO3—Bi0.5K0.5TiO3 based piezoelectric ceramics. Those materials have a problem in that they have a depolarization temperature of 140° C. or less at which a piezoelectric function is lost.
As another example, Japanese Patent No. 4510966 discloses a Bi0.5Na0.5TiO3—Bi0.5K0.5TiO3—BaTiO3 based piezoelectric ceramics having a piezoelectric constant d33 of 100 pC/N or more and having a decrease rate of the piezoelectric constant d33 of 15% or less in a high temperature storage test of 150° C. The maximum piezoelectric constant d33 of those materials when a decrease rate thereof is 15% or less is 134 pC/N.
As still another example, “Materials Chemistry and Physics” 2009, Vol. 114, pp. 832-836 discloses a Bi0.5Na0.5TiO3—Bi0.5K0.5TiO3—BiFeO3 based piezoelectric ceramics. The maximum piezoelectric constant d33 of this material is as large as 170 pC/N or more, but this material has a problem of a low electric insulation property because Fe is excessively dissolved in solid.